scholarly journals The effects of oscillating boundary conditions on thermal ignition

2020 ◽  
Vol 61 ◽  
pp. C45-C58
Author(s):  
Matthew Berry ◽  
Mark Nelson ◽  
Brian Monaghan ◽  
Ben Whale
Keyword(s):  
Temperature Variation ◽  
Filter Cake ◽  
Seasonal Temperature ◽  
Ambient Conditions ◽  
Ambient Temperatures ◽  
Temperature Oscillations ◽  
Seasonal Temperature Variation ◽  
Oscillating Boundary ◽  
Diurnal Temperature Variation ◽  
Ignition Times

We investigate the effect that oscillating ambient temperatures have on the ignition times of supercritical stockpiles. Large stockpiles are exposed to seasonal and diurnal temperature variation. We analyse the effects of seasonal temperature variation. When considering ignition within a year of construction, stockpiles built in spring ignited with a lower critical parameter than those built at other times. Consequently, seasonal temperature variation needs to be accounted for when predicting stockpile ignition times. References P. C. Bowes. Self-heating: evaluating and controlling the hazards. Dept. of the Environment, Building Research Establishment, 1984. R. J. Longbottom, B. J. Monaghan, G. Zhang, D. J. Pinson, and S. J. Chew. Self-sintering of BOS filter cake for improved recyclability. ISIJ Int., 59(3):432–441, 2019. doi:10.2355/isijinternational.ISIJINT-2018-627. V. Novozhilov. Thermal explosion in oscillating ambient conditions. Sci. Rep., 6:29730, 07 2016. doi:10.1038/srep29730. N. C. Roy. Convection characteristics in a closed vessel in the presence of exothermic combustion and ambient temperature oscillations. Int. J. Heat Mass Trans., 116:655–666, 2018. doi:10.1016/j.ijheatmasstransfer.2017.09.058.

scholarly journals About the penetration of the diurnal and annual temperature variation into the subsurface

2019 ◽  
Vol 2 (1) ◽  
pp. 1-5
Author(s):  
Günter Buntebarth ◽  
Maria Pinheiro ◽  
Martin Sauter
Keyword(s):  
Temperature Gradient ◽  
Surface Temperature ◽  
Temperature Variation ◽  
Test Site ◽  
Flow Density ◽  
Seasonal Temperature ◽  
A Value ◽  
Seasonal Temperature Variation ◽  
Diurnal Temperature Variation ◽  
University Of Göttingen

In order to evaluate the effect of the penetration of diurnal and annual wave temperature into the subsurface, the temperature has been monitored at an hourly recording frequency at depths of 40, 60 and 78 m between summer 2016 and summer 2018, at the geothermal experimental test site “Neutra” of the Georg-August-University of Göttingen, Germany. It has been asserted that the mean temperature gradient between 40 and 78 m continuously increases, because the temperature decreases at 40 m. The decrease can be explained by an increase in vegetation cover (trees, shrubs, etc.) in the perimeter of the test area, increasing the absorption of solar energy by the leaves. During the phenological growth season the diurnal temperature variation at the surface can be recorded in phase with opposite sign, even at a depth of 40 m, and the drop of the temperature at 40 m, when surface temperature reaches a value of nearly 9 °C, can be observed during small events of eco-dormancy during winter. The annual surface temperature variation of ±10 K induce the same effect with an amplitude of ±2mK at 40 m. It is stated that the dormant state of the vegetation cells is the reason of the annual variation of the residual temperature. At greater depths groundwater flows prevail and influence the temperature according to the structural properties of the encountered lithologies and the precipitation. The vegetation can transfer the daily and seasonal temperature variation to larger depths than expected based on the theory of heat conduction. This timely variation of the temperature gradient demonstrates that the determination of the terrestrial heat flow density is subject to several impacts induced from the surface as well as from the Earth’s interior. As a conclusion, temperature gradients determined at shallow depths may be influenced by changes in surface coverage.

scholarly journals Metagenomic Insights into the Effects of Seasonal Temperature Variation on the Activities of Activated Sludge

2019 ◽  
Vol 7 (12) ◽  
pp. 713 ◽  
Author(s):  
Chenbing Ai ◽  
Zhang Yan ◽  
Han Zhou ◽  
Shanshan Hou ◽  
Liyuan Chai ◽  
...  
Keyword(s):  
Microbial Community ◽  
Glutamine Synthetase ◽  
Activated Sludge ◽  
Temperature Variation ◽  
Nitrogen Metabolism ◽  
Metagenomic Data ◽  
Seasonal Temperature ◽  
Simulated Temperature ◽  
Genes Encoding ◽  
Seasonal Temperature Variation

It is well acknowledged that the activities of activated sludge (AS) are influenced by seasonal temperature variation. However, the underlying mechanisms remain largely unknown. Here, the activities of activated sludge under three simulated temperature variation trends were compared in lab-scale. The TN, HN3-H, and COD removal activities of activated sludge were improved as temperature elevated from 20 °C to 35 °C. While, the TN, HN3-H, COD and total phosphorus removal activities of activated sludge were inhibited as temperature declined from 20 °C to 5 °C. Both the extracellular polymer substances (EPS) composition (e.g., total amount, PS, PN and DNA) and sludge index of activated sludge were altered by simulated seasonal temperature variation. The variation of microbial community structures and the functional potentials of activated sludge were further explored by metagenomics. Proteobacteria, Actinobacteria, Acidobacteria and Bacteroidetes were the dominant phyla for each activated sludge sample under different temperatures. However, the predominant genera of activated sludge were significantly modulated by simulated temperature variation. The functional genes encoding enzymes for nitrogen metabolism in microorganisms were analyzed. The enzyme genes related to ammonification had the highest abundance despite the changing temperature, especially for gene encoding glutamine synthetase. With the temperature raising from 20 °C to 35 °C. The abundance of amoCAB genes encoding ammonia monooxygenase (EC:1.14.99.39) increased by 305.8%. Meanwhile, all the enzyme genes associate with denitrification were reduced. As the temperature declined from 20 °C to 5 °C, the abundance of enzyme genes related to nitrogen metabolism were raised except for carbamate kinase (EC:2.7.2.2), glutamate dehydrogenase (EC:1.4.1.3), glutamine synthetase (EC:6.3.1.2). Metagenomic data indicate that succession of the dominant genera in microbial community structure is, to some extent, beneficial to maintain the functional stability of activated sludge under the temperature variation within a certain temperature range. This study provides novel insights into the effects of seasonal temperature variation on the activities of activated sludge.

scholarly journals The impact of seasonality on niche breadth, distribution range and species richness: a theoretical exploration of Janzen's hypothesis

2016 ◽  
Vol 283 (1835) ◽  
pp. 20160349 ◽  
Author(s):  
Xia Hua
Keyword(s):  
Temperature Variation ◽  
Empirical Studies ◽  
Tropical Species ◽  
Seasonal Temperature ◽  
Thermal Niche ◽  
Trade Offs ◽  
Seasonal Temperature Variation ◽  
Latitudinal Patterns ◽  
The Tropics ◽  
The Impact

Being invoked as one of the candidate mechanisms for the latitudinal patterns in biodiversity, Janzen's hypothesis states that the limited seasonal temperature variation in the tropics generates greater temperature stratification across elevations, which makes tropical species adapted to narrower ranges of temperatures and have lower effective dispersal across elevations than species in temperate regions. Numerous empirical studies have documented latitudinal patterns in species elevational ranges and thermal niche breadths that are consistent with the hypothesis, but the theoretical underpinnings remain unclear. This study presents the first mathematical model to examine the evolutionary processes that could back up Janzen's hypothesis and assess the effectiveness of limited seasonal temperature variation to promote speciation along elevation in the tropics. Results suggest that trade-offs in thermal tolerances provide a mechanism for Janzen's hypothesis. Limited seasonal temperature variation promotes gradient speciation not due to the reduction in gene flow that is associated with narrow thermal niche, but due to the pleiotropic effects of more stable divergent selection of thermal tolerance on the evolution of reproductive incompatibility. The proposed modelling approach also provides a potential way to test a speciation model against genetic data.

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